Hello Burgo60 and Mowerfreak.
Yes, this was an ungoverned carburettor.
The parts list make it clear all 2-stroke Imperials had an identical motor.

That parts list is available as part of the Record for this machine:-

https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=72729

The engine was special in that it had an engine compression spacer
and a heavily modified G3 carby.

Burgo, I hope you sort out the issues here.

Cheers
Jack